[121.08] Why Does Intermittency of Supersonic Turbulence Not Affect Its Kolmogorov Spectrum?

H_20 masers in star forming regions are ideal probes of the highly
supersonic turbulence generated by outflows from the newly born stars
in the surrounding gas. They demonstrate: strikingly similar
dependence of the mean square velocity increment on
point separation l to the classic Kolmogorov 2/3 law for
incompressible turbulence and (2) a fractal pattern of the geometrical
set on which turbulence dissipates, with a very low fractal dimension
(D < 1). Yet, according to current understanding, both the energy
dissipation in large-scale shock waves and the intermittency of
dissipation (expressed by the fractal structure) should steepen the
dependence of on l, the steepening growing with
the decrease of fractal dimension. It has been argued before that
energy dissipation in large-scale shocks may be hindered, if the
vortical component of the flow is dominant due to appropriate boundary
conditions. Here we address the second question: why does the
low-fractal-dimension intermittency not steepen the velocity spectrum?
The approach to incompressible turbulence proposed recently by
Barenblatt amp; Chorin (Bamp;C) may lead to an answer. These authors argue
that intermittency doesn't disturb, but in fact helps to establish the
Kolmogorov law for the second and third order structure functions of
turbulence, when the Reynolds number tends to infinity. We show that
the Bamp;C approach is applicable to highly supersonic turbulent flows as
well as to incompressible flows and that the Reynolds numbers of the
supersonic turbulence probed by H_2O masers are very high indeed.
Further development of the theory of supersonic turbulence requires
elucidation of the role of a high Mach number and a study of the
behavior of higher order structure functions.

The author(s) of this abstract have provided an email address for comments about the abstract: bholder@wesleyan.edu